You could do it, but it would taste bad. Store purchase 'long-life' milks (almond, coconut, soy) all contain tiny amounts of preservatives which can give a bubbly effect when brought to boiling temperature, and it starts to smell bad. I know for a fact that sweetened almond milk from the store congeals and goes thicker when I heat it up whereas just water filtered almonds is closer to water and less of a 'milk'.

Works out cheaper as well if you buy bulk almonds and use your own water You can make a few litres in 20 minutes